An imaging apparatus having an optical lens performs imaging by image-forming an object image on a film, an imaging device, etc. by the optical lens. At this time, a phenomenon, which is referred to as shading, is produced, in which the brightness of the formed image is gradually decreased from the center of the lens to the peripheral area, according to the optical characteristic of the lens and the imaging area of the imaging device. In order to eliminate the shading in a digital still camera etc., methods for correcting the brightness of the imaged image data have been discussed, for example, in Japanese Unexamined Patent Publication No. 2000-134631 and No. 2004-289746.
As an example of the brightness correction, in the manufacturing process of the imaging apparatus, there are executed a process of imaging an object having a uniform brightness, and detecting an attenuation amount of the brightness according to the distance from the center of the imaged image, and a process of generating a brightness correction table, having a correction parameter according to the brightness attenuation amount stored therein, and storing it into a rewritable memory. When a user images, an image processing apparatus in the imaging apparatus corrects the brightness of the imaged image data using the correction parameter read out from the brightness correction table.
The brightness attenuation characteristic of the imaged image caused by the shading is different dependent on the optical characteristic of the lens and the imaging area of the imaging device. Therefore, for example, in such a case that the user exchanges an original lens to another lens having a different optical characteristic after the shipment of the imaging apparatus, appropriate correction is not made if the originally stored brightness correction table is used. Also, if a data stored in the memory is rewritten or erased, the brightness correction becomes difficult to be made. In such cases, it will lead to the increase of work and cost on the manufacturer side to reset the brightness correction table by collecting the imaging apparatus, besides causing user inconvenience.